Wilson Corners Solid Waste Management Unit (SWMU) 001: 2021 Annual Long-Term Monitoring Report, Kennedy Space Center, Florida

This report presents a summary of the long-term monitoring (LTM) activities that occurred in
2021 at Wilson Corners, Solid Waste Management Unit (SWMU) 001, at Kennedy Space Center
(KSC), Florida. The site is monitored under KSC’s Resource Conservation and Recovery Act
(RCRA) Corrective Action Program. Adaptive site management is being utilized through
ongoing assessment, design, and interim measures (IM). Annual LTM of the groundwater is also
being conducted at the site. This approach also meets the requirements of Chapter 62-780,
Florida Administrative Code (F.A.C.).

The goal of LTM at this site is threefold: to determine groundwater flow characteristics, monitor the downgradient concentration trends, and monitor select locations internal to the groundwater plume. Every 5 years, upgradient and side-gradient monitoring wells are sampled to verify delineation. The last time this was performed was in 2015. The sampling of these wells in 2020 was replaced with the direct push technology (DPT) investigations completed in October 2020 and April 2021. This DPT groundwater data was presented in an Advance Data Package (ADP) in September 2021 and discussed in the Implementation Work Plan (IWP) dated November 2021 for installation of an air sparge (AS) system. Based on results from groundwater sampling activities performed during the previous reporting period, including the 2020 and 2021 DPT groundwater sampling, it was determined that the LTM sampling plan was no longer meeting the goal of LTM because delineation was not verified. The 2021 LTM sampling plan was modified to include the sampling of monitoring wells located around the perimeter of the low concentration plume (LCP); the area with concentrations of contaminants of concern [COCs] greater than Groundwater Cleanup Target Levels [GCTLs]), and sampling of 10 monitoring wells proposed for installation (April 2021 KSC Remediation Team (KSCRT) Meeting, Decision 2104-D32). The modified LTM plan received team consensus at the September 2021 KSCRT Meeting (Decision Number 2109-D03), and sampling of the existing monitoring wells was completed in December 2021. The proposed monitoring wells are planned for installation in late 2022, concurrent with ongoing IM construction activities. December 2021 LTM data was presented at the May 2022 KSCRT Meeting, and activities are summarized in this report.

The activities presented in this report include the December 2021 groundwater gauging of 42
monitoring wells and sampling of 44 monitoring wells. During the December 2021 event, the
low flow sampling method was used, and samples were analyzed for a select list of volatile
organic compounds (VOCs), including 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113).

The following conclusions can be made based on the 2021 LTM results:
- In December 2021, groundwater flow for the site was generally to the west at all intervals.
This is generally consistent with historical observations at the site, with the exception of a
southwest and southeast flow component observed at 34 to 48 feet below land surface (bls).
- The vertical extent of VOCs was historically delineated by monitoring wells screened greater
than 48 feet bls. The results from the two vertical extent monitoring wells, WILC-MW0078
(screened 65 to 70 feet bls) and WILC-MW0130 (screened 56 to 66 feet bls) that were
sampled during the 2021 LTM indicate that groundwater vinyl chloride (VC) concentrations
in both wells were greater than the GCTL. The Remediation Team has previously agreed to
delay deeper DPT investigations in this area to prevent the creation of additional pathways
for vertical migration.
- The LCP continues to extend both horizontally, predominantly to the west, and vertically
beyond the current monitoring well network, with some retraction observed to the southeast.
Evaluation of this data combined with data from the 2020 and 2021 DPT sampling event
indicate that the LCP encompasses an estimated 20.7 acres based on an expanded sampling
area, as compared to the 2020 LCP footprint of 17.0 acres.
- Freon 113 was not detected above GCTLs during the 2021 LTM event.

Based on groundwater sampling activities performed in 2021, including April 2021 DPT
groundwater sampling, the following recommendations are provided:
- Perform the next LTM sampling event, targeted to occur in 2023, concurrently with the IM
baseline sampling prior to AS system installation;
- Include sampling from nine monitoring wells that are planned to be installed in late 2022,
concurrent with upcoming IM construction activities. Installation of one deep vertical well,
screened 70 to 80 feet bls, will be delayed to prevent the creation of an additional pathway
for vertical migration;
- Continue to sample under the modified annual LTM plan as presented in Table 4-1
concurrently with IM baseline sampling; and
- Once the AS system install and start-up is complete, select monitoring wells from the LTM
program will transition into the performance monitoring plan, and LTM will be temporarily
discontinued. Performance monitoring will be performed quarterly, and the monitoring well
network will be evaluated following the first performance monitoring sampling event.